<!DOCTYPE html>  
<html lang="en">  
<head>  
<meta charset="UTF-8">  
<meta name="viewport" content="width=device-width, initial-scale=1.0">  
<title>Hollow Circle Example</title>  
<style>  
  .hollow-circle {  
    width: 50px;  
    height: 50px;  
    border-radius: 50%;  
    border: 10px solid #3498db; /* 外圈边框 */  
    box-shadow: inset 0 0 0 5px #fff; /* 内圈空白，使用白色背景 */  
  }  
</style>  
</head>  
<body>  
  
<div class="hollow-circle"></div>  
  
</body>  
</html>